The present invention relates to the field of resetting a data processor and, more particularly, to the field of managing different classes of resets in a data processor.
All data processing systems need the capability of resetting under certain conditions, such as during power up or when certain errors occur. Without resets there would be no way to set the data processing system into a known state either to begin initialization routines or to begin error recovery routines.
The problem with resets, however, is that they have wide-ranging effects. In general, resets disrupt the normal flow of instruction execution and may cause a loss of data or information. Sometimes such drastic action is required to prevent more serious problems, but often the effect of the resets is worse than the condition which caused the resets.
Another problem with resets in conventional machines is that they are not localized. In other words, an entire data processing system is reset when only a portion needs to be. This is particularly a problem in systems employing multiple processors such as for fault-tolerant applications. In such systems, an error in one of the processors can propagate to the other processors and bring the entire system to a halt. If the originating processor was in error in generating resets, then the effect is to cause an unnecessary halt in execution.
It would therefore be advantageous to design a system in which the resets are matched to the conditions which generated the reset.
It would also be advantageous for such a system to have several classes of resets with different effects.
It would be additionally advantageous if, in a multiple processor data processing system, the resets in one of the processors did not automatically propagate to the other processors.
Additional advantages of this invention will be set forth in part in the description which follows and in part will be obvious from that description or may be learned by practicing the invention. The advantages may be realized by the methods and apparatus particularly pointed in the appended claims.